This disclosure relates to voice sensing, and in particular, using the microphones of an active noise reduction system to detect the voice of the system's user.
U.S. Pat. No. 8,682,001, by Annunziato et al., incorporated here by reference, describes an in-ear active noise reduction (ANR) headset that includes two microphones in each earbud, one inside the acoustic system for providing feedback-based ANR, and one outside the acoustic system for providing feed-forward-based ANR. In a commercial product embodying that patent application, the Bose® QC® 20 Acoustic Noise Cancelling® headphones, a fifth microphone was provided, in the cable joint housing of the headphone cable, for picking up the user's voice for use in communications applications. Other in-ear headphone products tend to also include communications microphones somewhere in the headphone cable, rather than in the earbud, as do many on-ear and around-ear headphones.
Detecting the voice of a user of headphones is useful for at least two reasons. First, it provides near-end audio for transmitting to a communication partner. Second, headphones, and in particular ANR headphones, tend to distort how the user hears his own voice when speaking, which we refer to as self-voice. Playing back the user's own voice within the headphones, which we refer to as side-tone audio, allows the user to hear his voice, and properly modulate it for conversation either with an electronic communication partner or face-to-face. Providing an accurate side-tone requires good voice detection.